1. Field of the Invention
This invention relates to a magnetic tape cartridge comprising a cartridge casing and a single reel which is housed in the cartridge casing for rotation and around which a magnetic tape is wound, and more particularly to a structure of a reel stopper means for preventing rotation of the reel when the magnetic tape cartridge is not being used.
2. Description of the Related Art
As a recording medium for use in an external memory of a computer or the like, there has been known a magnetic tape cartridge comprising a magnetic tape wound around a single reel and a cartridge casing in which the reel is housed for rotation. Since the magnetic tape is used for storing data in a computer or the like and important information is stored on the magnetic tape, the magnetic tape cartridge is provided with a reel stopper means which prevents rotation of the reel when the magnetic tape cartridge is not being used, e.g., when the magnetic tape cartridge is being stored, so that trouble such as tape jam does not occur and the magnetic tape is not accidentally drawn out.
The reel stopper means is provided with a brake member which is adapted to be engaged with the reel to prevent rotation of the reel and is disengaged from the reel to permit rotation of the reel in response to a reel chucking action of the reel drive means of a tape drive such as an external memory when the magnetic tape cartridge is loaded in the tape drive.
In order to improve reliability of the action of the reel stopper means and to prevent dust from entering the cartridge casing, the reel stopper means may be, for instance, of a structure comprising a brake member which restricts rotation of the reel, an urging member which urges the brake member toward a locking position in which the brake member restricts rotation of the reel, and a release member which is moved in response to a reel chucking action of the reel drive means of a tape drive to move the brake member toward a release position in which the brake member releases the reel to permit rotation of the same.
That is, when the magnetic tape cartridge is not being used, the brake member locks the reel so that the reel is not accidentally rotated and the magnetic tape is not accidentally drawn out, and when the magnetic tape cartridge is loaded in a tape drive, the release member drives the brake member to release the reel in response to a reel chucking action of the reel drive means of the tape drive. In this state, the reel can be rotated and loading/unloading of the magnetic tape is permitted.
In such a structure, it is advantageous in simplifying the structure that the release member is adapted to be brought into abutment against a part of the reel drive means of the tape drive and the reel drive means pushes a part of the release member to drive the brake member to release the reel when the reel drive means chucks the reel. However, in this case, when the release member drives the brake member to release the reel, the brake member can be inclined as shown in FIG. 5 and the gear teeth on the brake member can be brought into contact with the rear teeth on the reel while the reel is rotated, which results in generation of noise, obstruction of rotation of the reel and unstable magnetic tape loading/unloading action.
As a cause of the brake member being inclined, that the brake member becomes off-centered and comes to be inclined when the brake member is moved to the locking position where the braking gear thereon is brought into engagement with an engagement gear on the reel and the brake member is moved to the release position in this state can be conceived. Further, that the brake member was incorporated in the magnetic tape cartridge inclined relative to the reel when the magnetic tape cartridge was assembled can be conceived.
When the braking gear teeth on the brake member are like sawteeth in shape and the surface of each tooth facing against the tape-unwinding direction of the reel is substantially normal, though rotation of the reel in the tape-unwinding direction can be surely prevented, there is fear that the magnetic tape is cut when the reel is rotated in the tape-winding direction due to drop impact when the magnetic tape cartridge drops.
That is, when the braking gear and the engagement gear are engaged with each other at a substantially normal surface facing against the tape-unwinding direction, the reel cannot be rotated in the tape-unwinding direction. Further, a leader member such as a leader pin is fixed to the end of the magnetic tape wound around the reel, and the leader member is held near the tape draw-out opening of the cartridge casing when the magnetic tape cartridge is not being used. When the brake member is moved and the braking gear is disengaged from the engagement gear due to drop impact with the reel rotated in the tape-winding direction under inertia, a tape winding force acts on the magnetic tape whose end is fixed by the leader member. Since the reel cannot be rotated in the tape-unwinding direction or the direction in which the tension on the magnetic is released, the tape winding force acting on the magnetic tape can stretch the tape to deteriorate the magnetic recording and reproducing characteristics, remove the leader member from the magnetic tape, cut the magnetic tape, or displace the leader member from the predetermined position to disable the regular tape draw-out action, thereby deteriorating the reliability of the magnetic tape cartridge.
In view of the foregoing observations and description, the primary object of the present invention is to provide a magnetic tape cartridge in which the braking gear of the reel stopper means is suppressed from being brought into contact with the reel when the reel stopper means is in the release position.
Another object of the present invention is to provide a magnetic tape cartridge in which the reel can be surely prevented from being rotated while occurrence of the magnetic tape being cut can be prevented when the magnetic tape cartridge is not being used.
In accordance with a first aspect of the present invention, there is provided a magnetic tape cartridge comprising a magnetic tape wound around a single reel, a cartridge casing in which the reel is housed for rotation and a reel stopper means which locks the reel not to rotate when the magnetic tape cartridge is not being used and releases the reel to permit rotation thereof when the magnetic tape cartridge is to be used, wherein the improvement comprises that the reel stopper means comprises a braking member which is movable between a locking position where it is in contact with the reel to restrict rotation of the reel and a releasing position where it is away from the reel to permit rotation of the same, an urging member which urges the braking member toward the locking position, and a releasing member which is rotated integrally with the reel and moves the braking member toward the releasing position in response to a reel chucking action of the reel drive means of a tape drive, and the braking member is provided with a braking gear which is adapted to be engaged, to restrict rotation of the reel, with an engagement gear tooth on an engagement projection formed on the reel while the reel is provided with a guide member which centers the braking member with respect to the reel.
It is preferred that the guide member comprises guide ribs which are formed on the inner surface of the reel hub at at least three places, each having an inclined surface which inclines downward from the upper portion of the inner surface of the reel hub toward the center of the reel.
In the magnetic tape cartridge in accordance with the first aspect of the present invention, when the braking member is moved downward from the releasing position to the locking position, the braking member is centered by the guide members so that the braking gear is brought into mesh with the engagement gear teeth with the braking member held horizontal, whereby the braking member is prevented from being inclined in the locking position. When the braking member is subsequently moved to the releasing position by the releasing member, the braking member is held horizontal up to the releasing position. Accordingly, the phenomenon that the braking member is inclined can be suppressed, whereby the braking gear is prevented from contacting the engagement gear teeth to generate noise or to obstruct rotation of the reel.
Further, during assembly of the magnetic tape cartridge, the braking member is automatically centered in the reel hub by the guide members and is incorporated in place in the reel, whereby assembly of the magnetic tape cartridge is facilitated.
In accordance with a second aspect of the present invention, there is provided a magnetic tape cartridge comprising a magnetic tape wound around a single reel, a cartridge casing in which the reel is housed for rotation and a reel stopper means which locks the reel not to rotate when the magnetic tape cartridge is not being used and releases the reel to permit rotation thereof when the magnetic tape cartridge is to be used, wherein the improvement comprises that the reel stopper means comprises a braking member which is movable between a locking position where it is in contact with the reel to restrict rotation of the reel and a releasing position where it is away from the reel to permit rotation of the same, an urging member which urges the braking member toward the locking position, and a releasing member which is rotated integrally with the reel and moves the braking member toward the releasing position in response to a reel chucking action of the reel drive means of a tape drive, and the braking member is provided with a braking gear which is adapted to be engaged, to restrict rotation of the reel, with an engagement gear on an engagement projection formed on the reel, the outer diameter of the engagement gear being larger than that of the braking gear.
In the magnetic tape cartridge in accordance with the second aspect of the present invention, when the braking member is moved downward from the releasing position to the locking position, the braking member is centered by the difference between the outer diameters of the engagement gear and the braking gear so that the braking gear is brought into mesh with the engagement gear teeth with the braking member held horizontal, whereby the braking member is prevented from being inclined in the locking position. When the braking member is subsequently moved to the releasing position by the releasing member, the braking member is held horizontal up to the releasing position. Accordingly, the phenomenon that the braking member is inclined can be suppressed, whereby the braking gear is prevented from contacting the engagement gear teeth to generate noise or to obstruct rotation of the reel.
In accordance with a third aspect of the present invention, there is provided a magnetic tape cartridge comprising a magnetic tape wound around a single reel, a cartridge casing in which the reel is housed for rotation and a reel stopper means which locks the reel not to rotate when the magnetic tape cartridge is not being used and releases the reel to permit rotation thereof when the magnetic tape cartridge is to be used, wherein the improvement comprises that the reel stopper means comprises a braking member which is movable between a locking position where it is in contact with the reel to restrict rotation of the reel and a releasing position where it is away from the reel to permit rotation of the same, an urging member which urges the braking member toward the locking position, and a releasing member which is rotated integrally with the reel and moves the braking member toward the releasing position in response to a reel chucking action of the reel drive means of a tape drive, the braking member is provided with a braking gear which is adapted to be engaged, to restrict rotation of the reel, with an engagement gear tooth on an engagement projection formed on the reel, and each of the gear teeth of the braking gear has a first inclined surface which is brought into abutment against the engagement gear teeth when the reel is rotated in the tape-unwinding direction with the braking gear and the engagement gear tooth in mesh with each other and a second inclined surface which is brought into abutment against the engagement gear teeth when the reel is rotated in the tape-winding direction with the braking gear and the engagement gear tooth in mesh with each other, the first and second inclined surfaces forming therebetween an apical angle not larger than 90xc2x0, and the interior angle between the first inclined surface and the vertical being not larger than the interior angle between the second inclined surface and the vertical.
In the magnetic tape cartridge in accordance with the third aspect of the present invention, since the apical angle of the braking gear tooth is not larger than 90xc2x0 and the interior angle for the first inclined surface of the braking gear tooth which is brought into abutment against the engagement gear teeth when the reel is rotated in the unwinding direction and the interior angle for the second inclined surface which is brought into abutment against the engagement gear teeth when the reel is rotated in the winding direction are not smaller than 30xc2x0 with the former smaller than the latter, rotation of the reel can be surely prevented and when the reel is rotated in the winding direction due to drop impact or the like and an excessive winding force acts on the magnetic tape, the braking member is moved toward the releasing position along the first inclined surface and the braking gear is disengaged from the engagement gear teeth, whereby the reel is rotated in the unwinding direction to reduce the tension on the magnetic tape, and the magnetic tape can be prevented from being stretched or cut.